ใครช่วยเขียนโค้ด PHP ให้หน่อยครับเรื่องของการทำซ้ำ????

<?php
$sum = 0;
for($i=3;$i<=99;$i+=3){
$sum += $i;
}
echo $sum;
?>

$Num = 0
$Num += 3
$Num += 6
$Num += 9
$Num += 12
$Num += 15
$Num += 18
$Num += 21
$Num += 24
$Num += 27
$Num += 30
$Num += 33
$Num += 36
$Num += 39
$Num += 42
$Num += 45
$Num += 48
$Num += 51
$Num += 54
$Num += 57
$Num += 60
$Num += 63
$Num += 66
$Num += 69
$Num += 72
$Num += 75
$Num += 78
$Num += 81
$Num += 84
$Num += 87
$Num += 90
$Num += 93
$Num += 96
$Num += 99
echo $sum; 

<?php
$sum = 0;
for($i=3;$i<=99;$i+=3){
echo "$sum + $i = ";
$sum += $i;
echo "$sum<br>";
}
echo "<br><br><br><font color='red'>$sum</font>";
?>